1. Field of the Invention
The invention relates to a sawtooth wire for producing an all-steel sawtooth arrangement for processing textile fibers, in particular, for producing an all-steel sawtooth arrangement for a stripper of a carding machine with a plurality of teeth arranged successively in the longitudinal direction of the wire, wherein each tooth has a tooth breast beginning at the tooth bottom and extending in the direction toward the tooth tip and a tooth back extending from the tooth tip in the direction of the successively arranged tooth bottom.
2. Description of the Related Art
A carding machine is used in the production of yarns for the purpose of aligning and cleaning the textile fibers for forming the yarns. For this purpose, the textile fibers are supplied by means of a supply roller, a so-called swift. This is a roller-shaped element which is provided on its mantle surface with a hook arrangement or all-steel sawtooth arrangement and is rotated about the roller axis. The swift arrangement effects together with the card flat rods, distributed about the mantle surface of the swift, aligning and cleaning of the supplied textile fibers. After this process the fiber fleece obtained therewith is then supplied by means of a so-called stripper roller from the swift and transported to further processing stations. Conventionally, the stripper rollers are provided in the area of their mantle surface also with an all-steel sawtooth arrangement which, in the course of rotation of the stripper roller, engages the fiber fleece which is entrained by the swift and removes it from the swift.
Particularly in the processing of especially fine-denier fibers of natural or synthetic polymers it has been found that the transfer of the fiber fleece from the swift to the stripper roller presents problems. This results in a filling of the swift arrangement with fiber material that has not been removed and causes an unsatisfactory alignment and cleaning of the supplied textile fibers by the swift.
Moreover, it was found that the fiber fleece entrained by the stripper roller, particularly in the case of higher production weights, is prematurely removed from the stripper roller, and this can result in problems during further processing of the fiber material.
For eliminating these problems it has already been suggested to provide the sawteeth of the all-steel sawtooth arrangement of the stripper rollers with lateral rolled groove arrangements. This can be realized, for example, by a cold forming process during the course of the wire production wherein the sawteeth are stamped out of blade portions of the wire already provided with rolled groove arrangements. By means of these rolled groove arrangements a greater adhesion especially of fine-denier fibers of natural and synthetic polymers is achieved on the tooth flank. Accordingly, the transfer of the fiber fleece from the swift onto the stripper roller is positively affected in the sense that the transfer is quicker and the otherwise possible filling of the swift arrangement is prevented. Moreover, it was found that these lateral rolled groove arrangements, as a result of the increased greater adhesion of the fibers on the tooth flank, inhibit the premature detachment of the fiber fleece from the stripper roller.
It was however demonstrated that, in particular, for high output carding machines with production output of 80 kg or more in connection with the thus achieved high circumferential speeds of the stripper, despite the increased adhesive force as a result of the rolled groove arrangement in the tooth flanks, a premature detachment of the fiber fleece from the stripper occurs.
It is an object of the present invention to provide a sawtooth wire which makes possible the production of an all-steel sawtooth arrangement for the stripper of a carding machine and with which a premature detachment of the fiber fleece can be reliably prevented.
In accordance with the present invention, this is achieved in that the tooth back of at least one tooth of the sawtooth wire has at least one convex portion having a transition into a convex portion in the direction toward the tooth bottom.
In this context, the expression xe2x80x9cconcave portionxe2x80x9d refers to a portion of the tooth back whose successively arranged points are connected to one another only by straight lines positioned external to the sawteeth, while the expression convex portion refers to such edge courses whose successively arranged points are connected to one another by straight lines extending within the tooth flanks.
With the sawtooth wires according to the invention, an abutment for the fibers engaged by the stripper is provided by means of the transition of the convex portion into the concave portion in the area of the tooth back, and with the aid of the abutment a premature detachment of the fibers can be reliably prevented so that even for high production speeds a disturbance-free operation of the carding machine is made possible.
Even though it is also conceivable to provide this abutment by a depression in the course of the tooth back, wherein a concave portion is arranged between two convex portions of the tooth back, it has been found to be particularly beneficial when this abutment is provided by a projection or a cam in the area of the tooth back in which the convex portion forming a crown of the projection or the cam is arranged between two concave portions.
An especially high retaining force can be achieved when the tooth back of at least one of the teeth is provided with a plurality of convex portions each having a transition into a concave portion for obtaining a number of successively arranged depressions and/or projections or cams over the extension of the tooth back.
With respect to the fact that the all-steel sawtooth arrangement of the stripper engages usually in the area of individual tooth tips into the fiber fleece entrained by the swift, it was found to be especially favorable for obtaining a sufficient retaining force when at least one of the convex portions is arranged in the upper half of the tooth back adjoining the tooth tip, preferably in the upper third, particularly preferred in the upper fourth, of the tooth back.
Even though the concave portion as well as the convex portion can be provided in the form of progressions of straight-extending edge portions, it was found to be particularly beneficial with respect to obtaining a satisfactory retaining force, while simultaneously ensuring a gentle engagement of the fiber fleece, when the concave portion and/or the convex portion has a curved extension with a radius of curvature in the range of 0.05 to 0.4 mm, preferably 0.1 mm to 0.3 mm, particularly preferred approximately 0.2 mm.
In the context of the invention, it has also been considered to provide only individual sawteeth, for example, only every other, third or randomly selected sawtooth with a tooth back according to the invention. However, it has been found to be particularly beneficial when each tooth of the sawtooth wire has at least one convex portion having a transition into a concave portion in the direction toward the tooth bottom.
In sawtooth wires according to the invention an especially pronounced tooth tip of the individual sawteeth can be ensured when in at least one of the teeth the tooth breast has a concave breast portion forming a transition into the tooth tip and the tooth back has a convex portion adjacent to the tooth tip. With sawteeth formed in this way an especially reliable removal of the fiber fleece from the swift takes place.
Even though the tooth shape according to the invention already provides an especially high retaining force, in some cases, in particular, in the case of high output carding, it is required to provide an increase of this retaining force. In these cases, the embodiment of the sawteeth according to the invention can be combined with the known provision of rolled groove arrangements in the area of the tooth flanks so that at least one tooth flank, extending approximately parallel to the longitudinal direction of the wire, of at least one of the teeth has at least one profiling. This profiling can be at least one profiled groove extending approximately in the longitudinal direction of the wire and/or at least one profiled stay extending approximately in the longitudinal direction of the wire.
As has been explained in the beginning, sawteeth for processing textile fibers can be produced in that the starting material is shaped to a wire having blade portions and, subsequently, sawteeth are stamped into the blade portion. For producing sawtooth wires according to the invention, a tooth back can be produced on at least one of the sawteeth by the stamping process so as to have at least one convex portion having a transition into a concave portion in the direction toward the tooth ground. In addition, at least one flank of the blade portion, when forming the starting material, for example, by cold forming, can be provided with a profiling, like, for example, at least one groove extending parallel to the longitudinal direction of the wire and/or at least one stay extending parallel to the longitudinal direction of the wire.